In conventional calendered papermaking for providing paper substrates (e.g., paper sheets) used in printing, a fibrous web may be prepared from an aqueous solids mixture which may comprise wood pulp and/or synthetic paper fibers along with various additives such as sizing agents, binders, fillers, pigments, etc. Sizing agents are used primarily to prevent excess penetration, wicking, spreading, resistance to blotting etc., of water or ink, and especially internal absorption of the water or ink by the resulting paper substrate. Such sizing agents may include “internal sizing” agents in which the sizing agent (e.g., an alkyl ketene dimer, an alkenyl succinic anhydride, etc.) is included, added, etc., during the papermaking process before a fibrous paper substrate is formed, as well as “surface sizing” agents (e.g., starch, styrene maleic anhydride copolymers, styrene acrylates, etc.) in which the sizing agent is applied on, added to, etc., the surface of formed fibrous paper substrate. The sized paper substrate may exhibit improved properties in terms of, for example, print density, because more of the dye or pigment present in the ink remains on the surface of the paper substrate, rather than being absorbed internally by the paper substrate.
In recent years, the use of ink jet printing methods has been increasing at a rapid rate. Inkjet printing is a method for forming ink images on a paper substrate from deposited droplets of ink comprising dyes or pigments. This printing method enables high-speed and full-color printing to be achieved. In inkjet printing, the fine droplets of ink are sprayed or jetted from printing nozzles at a high speed so as to direct the ink droplets toward, and deposit these droplets on, the paper substrate to provide printed images on the paper substrate. The ink used in inkjet printing may contain either dyes or pigments as print agents. In the case of inks comprising pigments, the ink may also be in the form of a pigment emulsion.
Printed articles such as documents, books, direct mail advertising, etc., may be created by using web fed, higher speed inkjet printers. Examples of such higher speed inkjet printers may include, for example, Canon ColorStream 3000 printers, Ricoh InfoPrint 5000 printers, HP Pagewide Web Press T300, etc. Higher speed inkjet printers may be used to print such articles from paper substrates to save cost versus prior printing methods such as offset printing, laser printing, etc. To achieve such lower costs, customers may want to use low basis weight, lower cost printable paper substrates to create such printed articles when using inkjet printers, yet retain the desirable properties of higher basis weight, more expensive printable paper substrates, such as reduced or minimized showthrough. Showthrough is the phenomenon where the paper substrate may be printed on both sides, but becomes difficult to read on either side due to the print on one side “showing through” to the other side of the printed sheet.